The Islamist group led a fresh demonstration in Tahrir Square to protest against the army's decision to dissolve the Brotherhood-led parliament and seize veto powers over the constitution, announced just as their candidate Mohammed Morsi claimed victory in the weekend's presidential election. That army ruling renders the new president largely powerless, at least for the time being.

But the Brotherhood stepped back from mooted plans to force a confrontation at the parliament building, which was surrounded by troops and riot police. Just two MPs arrived to try to force their way in, but left after being repelled.

Yasser Ali, its spokesman, said: "We want to open a new page based on dialogue to rebuild Egypt. We don't want confrontation."

While the Brotherhood and Egyptian newspapers agree that Mr Morsi won around 52 per cent in the election, the campaign of his opponent Ahmed Shafiq once again claimed victory.

The interim government, the Supreme Council of the Armed Forces, and the Presidential Election Commission could still theoretically declare Mr Shafiq the winner at the official declaration on Thursday, stripping the Brotherhood of its second major organ of power in a week. That would undoubtedly reignite the possibility of conflict, possibly violent, between the Brotherhood's supporters, secular activists and the authorities.

Assuming Mr Morsi is confirmed as president, the stage is set for a new period of uneasy co-operation between the army and the Brotherhood. The army has reserved to itself a control over all military and security matters, and will have the legislative and budgetary powers of parliament until new elections.

But the presidency still has the right to form a government, which in Egypt has until now been independent of parliament.

Some of secular activist groups which led last year's revolution to oust Mubarak have put their weight behind the Brotherhood in its confrontation with the army.

As the evening progressed, thousands gathered chanting anti-army slogans, but it became clear that it would fall well short of the "million-man march" that had been called for.

The army's assertion of power, and a previous announcement last week that military police were being given the martial-law right to arrest civilians including protesters, have sparked concern from its traditional allies in the West.

After the Pentagon issued a strong-worded warning on Monday night, William Hague, the foreign secretary, yesterday issued a statement welcoming the peaceful conduct of the election but added: "The process of drafting a new, inclusive constitution and the holding of new parliamentary elections should be taken forward as soon as possible."